On Tuesday, November 6, 2012, we kicked off an activation reminder project aimed to stimulate growth on Yammer networks. This was a one-time email campaign where users (who were previously invited but had not yet accepted those invitations) were sent one last reminder.

Emails of this kind will not be sent to these users again, unless they are re-invited by an active user.

Despite our thorough checks and balances, we did not include the “user state” on one of the lines of code that ensures the user who sent the invitation originally is still an active user on the network. Because of that, some of these reminders were sent from inactive Yammer accounts.

We realize that this has caused some confusion and alarm. We can assure you this is not a security breach of any kind.

We apologize for any inconvenience this may have caused. Going forward, we have added steps to our checks and balances process that will prevent this from happening again.